Weighing cells that comprise a load cell are well known. See, for example, U.S. Pat. No. 4,479,561, assigned to the assignee of this application, the disclosure of which is incorporated herein by reference.
Commonly, such weighing cells include a platform for receiving an item to be weighed. A structure is interposed between the platform and the load cell for applying to the load cell the load resulting from the item's weight. The load cell is mounted upon a further structure which underlies the load cell.
The load cell provides a signal that represents the item's weight. The signal is received and processed by a scale's electronic circuitry, which provides a numerical value representing the item's weight. The numerical value is then displayed and/or used in a calculation or for another purpose.
When an item is placed on the platform, the weighing cell tends to oscillate for a period of time. The oscillation affects the signal provided by the load cell and also affects the numerical value provided by the circuitry. An accurate value for the item's weight is difficult to obtain until the amplitude of the oscillation falls below a given level. This is particularly important for low frequency oscillations. The period of time between placement of an item on the platform and provision of an accurate numerical value representing the item's weight is known as the scale's response time. It is often desirable to reduce the response time, particularly when a large number of items are to be weighed in a short period. As discussed in U.S. Pat. No. 4,787,048 (assigned to the assignee of this application) prior approaches to this problem have included mechanical structure that returns to a stable state relatively quickly and mathematical/statistical techniques that attempt to predict the weighing cell's ultimate stable state. U.S. Pat. No. 4,787,048 discloses use of a numerical value obtained while the amplitude of the oscillation remains relatively large in those cases where use of a relatively less accurate value is acceptable. The above referenced U.S. Pat. No. 4,479,561 discloses a weighing cell with energy absorbing feet which improve a scale's response time. While these approaches have merit, further reductions in response time are desirable, especially when load cell scales are to be incorporated in systems that are desired to have high throughput rates.